This invention relates to vibration compacting machines, and more particularly to an eccentric assembly for a vibration compacting machine.
Vibration compacting machines are used in leveling paved or unpaved ground surfaces. A typical vibration compacting machine includes one or two vibrating drum(s) that transfer vibrations to the ground. The eccentric assembly commonly includes one or more eccentric weights that are adjustable between a plurality of discrete radial positions relative to the shaft in order to vary the amplitude of the vibrations that are generated by rotating the eccentric weight(s) about the shaft.
One type of adjustable eccentric assembly operates by varying the rotational speed of the shaft. The eccentric assembly includes one or more eccentric weights that are biased toward the shaft. During operation of the eccentric assembly the shaft rotates, and as the rotational speed of the shaft increases, a centrifugal force overcomes the biasing force and causes the eccentric weight(s) to move away from the shaft. The vibration amplitude increases as the eccentric weights move away from the shaft.
Another type of device that is operable between a first mode having a high amplitude vibration and a second mode having a low amplitude vibration includes a plurality of eccentric weights that are fixed to the shaft and a corresponding number of counterweights that are coupled to the opposite side of the shaft relative to the eccentric weight. The counterweights are moveable between a retracted position and a projected position relative to the longitudinal axis of the shaft. When the counterweights are in the retracted position their effect on the eccentric weights is minimized resulting in maximum vibration amplitude being generated by the eccentric weights. The counterweights are normally biased toward the retracted position, however as the shaft rotates the biasing force is overcome and the counterweights are moved to the projected position where the counterweights are further away from the shaft. As the counterweights move further from the shaft, the counterweights reduce the effect of the eccentric weights resulting in a lower vibration amplitude.
The above-described eccentric assemblies are generally effective for creating vibration within vibration compacting machines. Therefore, any improvement to such eccentric assemblies would be desirable.
The present invention is directed to an eccentric assembly for a vibration compacting machine. The eccentric assembly of the present invention is rotated by a motor in order to generate vibrations that are transferred to the ground via a drum. The eccentric assembly rotates at high speeds in order to generate high frequency vibrations, and is configured to reduce the vibration amplitudes at such high frequencies. Reducing the amplitude of the vibrations at high vibration frequencies minimizes wear to each of the load bearing components in the vibration compacting machine resulting in an extended service life for the vibration compacting machine. The eccentric assembly of the present invention is also easily assembled, inexpensively manufactured, and readily adapted to be used in existing vibration compacting machines.
The eccentric assembly includes a shaft, first and second eccentric weights, and a member. The first and second eccentric weights are rotatably coupled to the shaft such that they generate vibrations which are transferred to the ground via the drum when the shaft is rotated by a motor. The eccentric weights are also coupled to the shaft by the member which moves the eccentric weights between a first position where the eccentric weights are in phase and a second position where the eccentric weights are out-of-phase. When the eccentric weights are in phase the eccentric assembly generates a maximum moment of eccentricity about the shaft. As the rotational speed of the shaft increases to higher frequency vibrations, the eccentric weights move out of phase reducing the moment of eccentricity. Reducing the moment of eccentricity at higher rotational speeds results in lower vibration amplitudes for the higher frequency vibrations.
The member is preferably biased toward the first or phased position by a spring. When the shaft is rotated at high enough speeds, a centrifugal force is generated on the member which overcomes the biasing force generated by the spring such that the member moves toward the second or out-of-phase position thereby lowering the moment of eccentricity.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.